docs: def dlls_in_dir(directory):
      """Returns *.dll, *.so, *.dylib in given directory."""
      files = []
      files.extend(glob.glob(os.path.join(directory, '*.so')))
      files.extend(glob.glob(os.path.join(directory, '*.dll')))
      files.extend(glob.glob(os.path.join(directory, '*.dylib')))
      return files